Method of adding magnesium to molten iron



United States Patent METHOD OF ADDING MAGNESIUM TO MOLTEN IRON James Fernando Jordan, Huntington Park, Calif., assignor of one-third to the estate of James Jordan, deceased No Drawing. Application February 12, 1951, Serial No. 210,623

3 Claims. (Cl. 75-130) My invention relates to the metallurgical process wherein magnesium is alloyed with molten iron.

In my application, Serial No. 172,009, which matured into Patent No. 2,543,853 on March 6th, 1951, I disclosed the advantages to be gained from the use of magnesium carbide as an addition agent in the manufacture of nodular iron. Magnesium carbide, together with the conventionally-employed alloys of magnesium with nickel, silicon, or copper, have the serious disadvantage that their density is such that they float on the surface of the molten iron, and, being quite reactive with air at elevated temperatures, these alloys and magnesium carbide all tend to be oxidized before the magnesium has an opportunity to alloy with the iron. The amount of magnesium that is oxidized by the air varies, depending upon the alloy and the degree of subdivision. While magnesium carbide is the best of these addition agents, its heat of formation is very low, with the result that it is very reactive with the air at high temperatures, for little of the reactivity of the magnesium is lost when magnesium combines with carbon to form the carbide. When large lumps of the carbide or alloy are employed, air oxidation offers little problem; similarly, when the carbide or alloy is immersed in the molten iron, air oxidation offers no problem. It is seldom feasible, however, to employ large lumps of the carbide or alloy, and immersion oifers serious problems in most cases.

The problem was to find a magnesium compound/ alloy that was quite non-reactive with air at elevated temperatures, so that the magnesium addition might be made by simply allowing the compound or alloy to float around on the surface of the molten iron until the magnesium content of the compound/alloy was taken up the iron; that released its magnesium content to the molten iron as magnesium gas, not liquid magnesium, for it is the expansion that accompanies the explosive evaporation of liquid magnesium which causes the addition of magnesium to molten iron to be such a dangerous affair; and, preferably, that was cheaper to produce than magnesium carbide.

I have found that magnesium cyanide, magnesium cyanamide and magnesium nitride meet these conditions, particularly the nitride. I have found that magnesium nitride floats around on the surface of the molten iron ICC without suflering any appreciable oxidation by the air, and I have found that the nitride gives up its magnesium content to molten iron as it floats thereupon. Magnesium cyanide and magnesium cyanamide act similarly. This ability of magnesium nitride, cyanide and cyanamide to form a magnesium-iron alloy upon being placed in contact with molten iron was an unexpected result, for it had been previously thought that a magnesium-iron alloy could not be formed unless the magnesium was added in a form that exhibited a high free energy-as the metal or alloy thereof, for example, or as a compound possessing a low heat of formation, such as the carbide.

In a test that I made, I added sufficient magnesium nitride to a bath of molten cast iron to yield an iron containing 0.10% magnesium if the pick-up was 100%. After the nitride disappeared from the surface of the molten iron, a sample was taken of the resulting iron. Analysis showed that the iron contained 0.093% magnesium, showing that little of the magnesium was lost. In other tests which I made, I found that a magnesium pick-up of at least could be depended upon when magnesium nitride was employed as the addition agent.

In other tests, I found that nitro-limethe cyanamideand magnesium cyanide could be similarly employed to add magnesium to iron to form a magnesium-iron alloy; however, it was observed that neither of these compounds was as effective as the nitride, apparently due to the fact that a portion of these compounds volatilized before cracking.

In other tests, I found that magnesium nitride was also an excellent addition agent for the formation of magnesium-bearing steel.

Having now described several forms of my invention, I wish it to be understood that my invention is not to be limited to the specific form hereinbefore disclosed, except insofar as such limitations are specified in the appended claims.

I claim as my invention:

1. The method of alloying magnesium with molten cast iron which comprises reacting magnesium nitride with said molten cast iron until said alloy is formed and casting the resulting molten cast iron.

2. The method of alloying magnesium with molten cast iron which comprises reacting a compound selected from the group consisting of magnesium nitride and magnesium cyanamide with said molten cast iron until said alloy is formed and casting the resulting molten cast iron.

3. The method of alloying magnesium with molten cast iron which comprises reacting magnesium cyanamide with said molten cast iron until said alloy is formed and casting the resulting molten cast iron.

References Cited in the file of this patent UNITED STATES PATENTS 1,335,370 Ellis Mar. 30, 1920 2,121,057 Smith June 21, 1938 2,552,204 Morrogh May 8, 1951 

1. THE METHOD OF ALLOYING MAGNESIUM WITH MOLTEN CAST IRON WHICH COMPRISES REACTING MAGNESIUM NITRIDE WITH SAID MOLTEN CAST IRON UNTIL SAID ALLOY IS FORMED AND CASTING THE RESULTING MOLTEN CAST IRON. 